1. Field of the Invention
The invention relates to a machine for producing various grades of a paper, board, tissue or of another web material, having a system for predefining the quantity of a grade to be produced.
2. Discussion of Background Information
DE 101 21 775 A1 discloses a method and apparatus for calibrating consistency sensors. During the production of a fibrous web, in particular, a paper or board web, sensors are used to measure the consistencies of the fibrous stock suspensions needed for the production process. According to the known system, the consistency sensors are calibrated online and automatically. In this case, the actual consistency values can be determined from the measured consistency values obtained, by means of at least one mass balance and by means of sensor characteristics. In one embodiment of the known system, use is also made of a consistency sensor which supplies the initial basis for the calibration of the other consistency sensors. Such a consistency sensor for measuring the actual consistency is, for example, a sensor for determining the grammage or the dry weight of the paper web after the latter has run through a press.
Enterprise Resource Planning (ERP) systems, which are widespread nowadays, take no account of electronic quality data or web inspection data which are measured during the production operation, that is to say online, which provide indications on defects or holes in the fibrous web. Therefore, it is not possible to make any predefinitions as to how much of one grade of a fibrous web should be produced.
Instead, the production planning is carried out in the following way: The ERP system predefines how much of a specific grade is needed. This target variable is then used as a target variable on the paper machine. The production management can increase this target variable in order to take account of the fact that part of the production may become broke on account of process fluctuations or defects. The finished parent reels, wound with the paper web, are transported from the paper machine to a slitter-rewinder. There, the parent reels are cut in accordance with the predefinitions and requirements of the final customers. Defects and other broke are cut out. In this case, quality measurements which were carried out on the paper machine are used to find the broke locations. By means of this procedure, the hope is to have produced sufficient to wind the quantity of “good production” required by the ERP system onto rolls determineed for the final customers, in spite of the broke produced. If this is not successful, a small quantity of paper has to be produced subsequently, which entails considerable additional costs because of the grade change times in the paper machine.